Dry Matter Intake and Beta-Hydroxybutyrate Response in a GTT in Phase Shifted Dairy Cows

<p>Supplemental figures from paper published in Journal of Dairy Science </p>

<p>Circadian and metabolic systems are interlocked and reciprocally regulated. To determine if the circadian system regulates glucose homeostasis and mammary development, the function of the circadian system was disrupted by exposing cattle to chronic light-dark cycle phase shifts from five wk before expected calving (BEC) to parturition. Multiparous Holstein cows were exposed to 16 h of light and 8 h of dark (CON, n=8) or phase shifting (PS, n=8) the light cycle 6 h every 3 d beginning 35 d BEC. After calving, both treatments were exposed to control lighting. Intravenous glucose tolerance test (IVGTT) was performed at 14 d BEC and 7 DIM by administering 50% dextrose. Blood β-hydroxybutyrate (BHB) was consequently measured over 3 h. Additionally, dry matter intake (DMI) was recorded for all cows between 35 d BEC through 21 DIM. At 14 d BEC and 7 DIM there were no treatment differences in BHB concentrations. Additionally, there was no difference in DMI between the treatments. Thereby indicating that light shifting circadian disruptions do not impact cattle BHB concentrations during an IVGTT or feed intake.</p>